Voltage regulator circuit



Sept. 2, 1952 l.. E RABURN ETAL VOLTAGE REGULATOR CIRCUIT j" Filed oqt. `11, 1949 N /.R @o T T A Patented Sept. 2, 1952 VOLTAGE REGULATOR CIRCUIT l Louis E. Raburn, Evansville, Ind., and John P. Woods, Dallas, Tex., assignors to the United States of America. as represented by the Secretary of the Army Application October 11, 1949, Serial No. 120,803

The invention described in the specication and claimsmay be manufactured and used by and for the Government for governmental purposes, without the payment to us of any royalty thereon.

This invention relates to electrical' apparatus in general and more particularly to improvements in voltage regulator circuits of the vacuum tube type. This application is a continuationin-part of application Serial No. 648,537, led

February 18, 1946, which has been abandoned.

Vacuum tube voltage regulator circuits are used where a substantially constant voltage output is required. One well known type of voltage regulator circuit is the so-called regenerative circuit.

In the so-called regenerative voltage regulator,

a current-regulating vacuum tube, whichjserves as a variable impedance, is placed in series with the line from an unregulated power supply to a load. The tube used may be any type having sulicient current carrying capacity. If neces` YfAnim'portant object of the present invention is the design of a variable output voltage regulator circuit, in which the voltage regulation is maintained over a wide range of output voltages. Other objects and advantages of the invention will be apparent during the course of the following description.

The present invention utilizes a potentiometer to vary the grid-to-cathode voltage of a control tube with the potentiometer ganged to an adjustable tap on a power input transformer. While the following description pertains to a regenerative type of voltage regulator circuit, the invention is not limited thereto.

The single figure of the accompanying drawing shows a simplified schematic diagram of a regenerative type of voltage regulator circuit which illustrates one possible embodiment of the present invention.

Referring to the figure, numeral I designates Z Claims. (Cl. 321-19) an A. C. input line. Power transformer II has a secondary winding I2, which has an adjustable contact to obtain a variable secondary output voltage. The secondary Winding I2 furnishes a variable A. C. voltage to a rectifier and lter circuit I3. The output of the rectier and lter circuit I3 is a variable unregulated D. C.voltage appearing at input terminals I4.

The remainder of the circuit is the voltage regulator proper.

Frequently, high voltage circuits require the positive voltage lead grounded and the negative voltage lead ungrounded. In the hereinafter described circuit the outputof the voltage regulator is a variable regulated D. C. output voltage with a grounded positive voltage lead appearing at output terminals ,20.

The invention, of course, may be applied as well to the regulation of power supplies where the negative output voltage lead is grounded.

A current-regulating'vacuum tube 2| is placed in the line between the rectier output and vthe load. This tube is shown as a triode, but any tube having the proper current carrying capacity may be used. The grid-to-cathode potential -of tube 2I is determined by the voltage drop across anode resistor 22 in the anode circuit of a control tube 23.

The cathode potential of control tube 23 is obtained from a voltage divider consisting of re sistors 24 and 25 which is connected across the output voltage. The cathode voltage of control tube 23 accordingly will be a function ofthe D.` C. output voltage.

A substantially constant potential with respect to ground is obtained at the cathode of voltage regulator tube 26, which, with its series resistor 2l, is placed across the D. C. output voltage. The potential at the grid of control tube 23 is obtained from a potentiometer 28, which is in parallel with voltage regulator tube 2S. This grid Voltage will be fairly constant despite variations in the D. C. output voltage. The adjustable contact of secondary winding I2 and the movable contact of potentiometer 28 are ganged together by means of connection `29.

The regulating action of the voltage regulator circuit shown in the figure will now be explained. The explanation will take the form of first explaining how regulation is accomplished with a fixed setting of the contact on secondary winding I2 for:

a. Variation of the A. C. input voltage.

b. Variation of the load resistance across the output terminals 20.

Suppose a surge in the A. C. input line I0 increases the regulated output voltage. This Will .then make the cathode of control tube 23 more lating tube 2l will decrease the regulated output voltage.

This regulating action tends toA maintain the D. C. output voltage substantially constant. l

Suppose the load across-the; regulator output decreases. A decrease in the load resistance will tend to cause a decrease inthe output voltage.

A decrease in the output voltage will make the` cathode of control tube 23 more positive; decreasing the current through, tube 23 and decreasing thevoltage drop across anode-resistor 22. A decreased voltage across anode resistor 22 decreases thenegativegrid bias of current-regulating,tube.2|,.thereby decreasingV the voltage drop across tube 2L and increasingthefoutput voltage. This regulating actionl tends to maintainV the D. C. output voltage substantially constant.

It is necessary to, alsok investigate the change in voltage regulation caused by adjustment of the contact on secondary Winding .|2. This adjustment would in itself be accompanied by a variationof the D. C. output voltage and by a diminished regulating action of the circuit. The regulating action of the circuit is maintained overv a Wide range of D, C. output voltages by potentiometer 2,8.which is ganged with the contact on transformer secondary winding l2. Suppose that .the contact setting on secondary. winding l2 is increased, resulting in an increased output voltage, and, because of the ganged potentiometer-28, in a decreased positive gridpotential for; controltube 23. The increased outputvoltage also causes the cathode potential or? control tube .23, to become more negative. Hence,v the negative grid bias of control tube 23 tends to remainconstant and consequently the regulating action of control tube y23 and current regulating tube 2| is maintained over a Wide range of input and output voltages.

Despite the simplified formY in which this circuit has been presented, it is obvious that the applications ofl this voltage regulator circuit are many. The current-regulating tube 2l may bea bank of tubes in parallel to assure the `necessary current rating.V A group of voltage regulator tubes in series may be substituted for the single tube shown if necessary to attain the proper grid voltage for control tube 23.

It will be apparent that there may be deviationsfromfthe invention as described which still fall fairly withinA the spirit and scope ofthe invention.

What is claimed is:

1. A power supply comprising first' and second input terminals; a source of unregulated direct current voltage having the positive potential side thereof connected to said rst input terminal and the negative potential side thereof connected to said second input terminal; voltage-control means coupled to said source for altering the magnitude of said unregulated voltage; a current regulator electron tube having at least a cathode, an.v anode. and a control electrode; first and second output terminals adapted to have a load connected thereacross; means connecting said firstinput'terminal to said first output terminal through the anode-cathode path of said current regulator tube; means connecting said second input terminaltoisaid second output terminal; a control tube having at least a cathode, an anode and acontrol electrode; means for applying a xed proportion of the voltage appearing across saidgoutputi terminals; to the; cathode. of said icontrol tube; means. shuntingsaid output terminals for obtaining a pointv of potential having'a fixed negativemagnitude relative tothe potential at said rst output terminal; a potentiometercon'- nected between said point of potential 'and said first output terminal; means for applying'the potential at the movable tapof said potentiometer to the control electrode ofA said control tube; a resistor connecting the anode of said control tube to a point having a positive potential relativeto the cathode thereof.; means for applying the potential at the anode of said control tube to the control electrode of said current regulator tube; and means gauging the movable tap of said potentiometer and said voltage control means to alter the magnitude of' thev voltage betweenl the movableA tap of said potentiometer and said first output terminalin the same directionv as the magnitude of said unregulated Voltage.

2. The power supply defined in claim l, wherein said means for obtainingA said point of'poten tial includes a gaseous discharge tubehaving its anode connected to said first output terminal, and a resistor connected betvveenthecathode of said gas discharge tube andA said second output terminal, said point of potential being at the junction of the cathode of said gaseousdscharge deviceand said last-named resistor.

Thefollowing references are of record in the leof this patent:

UNITED STATES PATENTS Name Date Wellons June 5, 1951 Number 

